Cellulose nanocrystals from blueberry pruning residues isolated by ionic liquids and TEMPO-oxidation combined with mechanical disintegration

Abstract

In the last years, Chile has increased the production of blueberries; consequently, a large number of lignocellulosic residues derived from the harvesting and pruning are being generated. These residues are commonly burned, therefore increasing CO₂ emissions. This study focuses on the extraction of two added-value products from blueberry pruning residues (BPRs), cellulose nanocrystals (CNC-IL) isolated using ionic liquid (IL) 1-ethyl-3-methylimidazolium [emim][Cl], and carboxylated nanocellulose (TOCNC), isolated with (2,2,6,6-tetramethylpiperidine-1-yl) oxyl or TEMPO reagent combined with a mechanical disintegration process. These products were characterized by zeta potential (ζ), FTIR, XRD, TGA, AFM, and conductometric titration. Results show oval-shaped CNC-IL particles with lengths of 46.1 ± 9.3 nm; meanwhile, TOCNC were rod-like shaped particles, with lengths of 120.3 ± 30.6 nm. These BPRs showed a promising potential to produce cellulose nanocrystals (CNCs) with different surface properties, opening a new alternative for the production of cellulose nanomaterials (CNMs) with promising applications in colloidal formulations, coatings, among others.

Graphical Abstract

Keywords:

• cellulose nanocrystals
• ionic liquid
• tempo oxidation
• blueberry residues

Acknowledgments

The authors would like to acknowledge the company Berries del Bio-Bio for supplying the BPRs, and the Department of Bioproducts and Biosystems, Aalto University (Espoo, Finland), the Center of Biomaterials and Nanotechnology (CBN) at Universidad del Bío-Bío, Chile, and Centro de Investigación de Polímeros Avanzados (CIPA) Chile for laboratory facilities and analysis techniques. C.P., also wants to acknowledge the postgraduate scholarship of VRIP, Universidad del Bío-Bío. Equally, the authors express their sincere gratitude to Dr. A. Fernández-Pérez, academic of the Department of Physics of the Universidad del Bío-Bío, Chile, for helping with the AFM analysis.